Deposition of films on a substrate surface is an important process in a variety of industries including semiconductor processing, diffusion barrier coatings and dielectrics for magnetic read/write heads. Chemical vapor deposition (CVD) and atomic layer deposition (ALD) are two deposition processes used to form or deposit various materials on a substrate. In general, CVD and ALD processes involve the delivery of gaseous reactants to the substrate surface where a chemical reaction takes place under temperature and pressure conditions favorable to the thermodynamics of the reaction. However, a common problem with one or more these deposition processes is the unwanted deposition onto deposition chamber walls, showerhead, etc. For example, if cobalt films are deposited, there is a possibility for the buildup of undesired cobalt metal or compounds (e.g., carbidic cobalt) on the walls of the chamber. It then becomes necessary to remove this buildup. There is thus a need for methods of cleaning such buildup from deposition equipment. In particular, it would be particularly advantageous to have self-limiting etch methods, which would yield greater control during etch.
Additionally, in the semiconductor industry, miniaturization requires atomic level control of thin film deposition to produce conformal coatings on high aspect structures. One method for deposition of thin films with control and conformal deposition is atomic layer deposition (ALD), which employs sequential, surface reactions to form layers of precise thickness. Most ALD processes are based on binary reaction sequences which deposit a binary compound film. Because the surface reactions are sequential, the two gas phase reactants are not in contact, and possible gas phase reactions that may form and deposit particles are limited. However, before the present invention, there has not been a commercially viable way to delicately etch films with control and conformality. For example, while there have been wet etch methods proposed for cobalt, there is still a need for dry methods to remove cobalt and/or cobalt residue, and preferably in situ methods that are self-limiting and allow for precise control over etch rate. Even more particularly, a method that is selective for a particular metal is desired, as it would provide even more control over the etching process.